In servicing cordless telephone systems, the accounting operation is conventionally done in a subscriber's line switchboard which receives a parent phone line. Present cordless telephone systems operate with private base stations at users' homes, offices or other locations which are connected to a public telephone system. Since each private base station is typically meant to be used only by one subscriber, the accounting operation that will be done in the subscriber's line switchboard would not be too complex.
In addition, since line connection is limited to a predetermined subscriber's line, there is a disadvantage in that it is impossible to move and utilize the telephone set over a broad area. In the next generation of cordless telephones (called CT-2, for cordless telephones, second generation) there will be a plurality of public base stations (also called telepoints) that may be used by any subscriber within range. When in range, a subscriber will be able to access the public switched telephone network (PSTN) and place a call. However, due to the increase in users, the traffic due to the accounting operation for these users in the public telephone network would consequently be multiplied. It is therefore, a desire to minimize the traffic due to increased billing and record keeping done at the public telephone network.
To partially alleviate this increased traffic in a typical CT-2 system, each public base station establishes communications with the CT-2 network control center (NCC) only once every 24 hours for an administrative session. During this session, the base station downloads call detail records of calls handled in the preceding 24 hours and uploads validation/barring data from the NCC. However, some CT-2 service providers do not want to have to wait at least 24 hours before a subscriber can be stopped for exceeding a particular charge limit. The service providers therefore desire a means for limiting the amount of charges that can accrue to a subscriber during a single billing cycle for certain types of calls, most notably, international direct dial (IDD) calls that are the most expensive.
One method for accomplishing a real-time IDD charge limit is to require a real time access to the NCC for permission before allowing the IDD call to go through, for every IDD call placed via the CT-2 base station. In addition, a second access to the NCC is required at the end of each IDD call in order to update the subscriber's IDD charge tally. However, this method of limiting IDD charges can cause a substantial increase in the administrative traffic of the public telephone network. Therefore, there is at least a need to control call charges with a minimum increase in traffic due to the accounting operation in the public telephone network if the billing and record keeping operation at the public telephone network cannot be totally eliminated.